This invention is related to the manufacture of color television display screens. The prior art manufacturing techniques are described in greater detail in U.S. Pat. No. 3,712,815 issued Jan. 23, 1973, entitled "Method of Manufacturing a Display Screen", and in U.S. Pat. No. 3,793,035, issued Feb. 19, 1974, entitled "Method of Developing Opaquely Coated Sensitized Matrix with Periodate Containing Solution", which patents are owned by the assignee of the present invention.
The aforementioned patents disclose a manufacturing technique in which a photosensitive layer is deposited upon a screen substrate and exposed to light through a conventional shadow mask to sensitize the photosensitive material in a selected pattern. An opaque coating is then applied over the entire screen, and the screen treated with a developing solution which includes a periodate containing compound which is readily soluble, and wherein the pH is adjusted to a predetermined range using selected reagents such as ammonium hydroxide and/or sulfuric acid.
While the aforementioned developing solution with the reagents mentioned has been found useful, the reagents are relatively harsh and require careful handling as well as being corrosive reagents with respect to the manufacturing equipment with which they come in contact. The use of relatively harsh reagents, such as ammonium hydroxide and sulfuric acid, can also degrade the opaque layer in the process of developing the photosensitized layer beneath the opaque layer. This opaque layer is intended to remain in the final color television picture tube in a relatively uniform thickness over selected areas of the screen. It is important in the developing process that the photosensitive material be removing as well as the opaque material atop the photosensitized portions, and that the remaining portions of the opaque layer upon the substrate be uniform and not be adversely affected by the developing solution.